PASTIME
IN 1760 HOROLOGIST JOHN HARRISON TOOK HIS 1735 INVENTION OF THE MARINE CHRONOMETER TO A HIGHER LEVEL BY MAKING IT PORTABLE IN THE FORM OF A POCKET WATCH – HIS H4 WAS EFFECTIVELY THE FIRST PRECISION WATCH AND THE TRUE ANCESTOR OF THE CHRISTOPHER WARD COLLECTION
Longitude Solution
The G
alileo, Cassini, Newton, Halley. Some of the greatest names in modern science
history tried, and failed, to solve what was described for centuries as “the longitude problem”. It came down in the end to
a self-taught horologist – a man who started out as a working class carpenter – to finally solve the problem in 1735, with the invention of the first ship’s chronometer. He refined and refined the design and mechanics until in 1760 he produced the first practical tool for ship’s navigation – a pocket watch sized device. Now 250 years on it seems
incredible that such a thing as the longitude problem ever existed. But exist it did: many sailors’ lives were still being lost decades into the 18th century – just as they had been lost during the earlier explorations in the 16th and 17th centuries – as a result of inaccurate navigation when ship’s travelled east or west.
While it was, and is, relatively easy to calculate position on the globe on a north to south axis using the sun or the stars and the lines of latitude, the east/west position – along the lines of longitude – could not be worked out in the same way because the earth is rotating.
Marine timekeeper, H4 – Harrison's prize-winning longitude watch, completed in 1760
Ships sometimes arrived at their destinations as much by luck as by good judgement, and returning to home ports was just as, and sometimes more, problematic. The Isles of Scilly off the south west coast of England were a notorious location for shipwrecks as ships’ captains simply got their positions wrong.
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There existed a theoretical solution based on measuring time, but until Harrison’s invention was proved an astronomical solution was still thought to be the most likely avenue even into the 18th century. The time solution suggested that in order for ships to keep track of their position, they needed both the time at the home port and the time on the ship. The problem was that in order to create a system that provided accurate navigation, time would have to be measured to an accuracy of seconds – because seconds of time can represent huge shifts in distance. This was a level of accuracy that
did not exist until Harrison’s breakthrough. Harrison understood that the longitude problem was not
National Maritime Museum, Greenwich, London, Ministry of Defence Art Collection
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